🧱 Cement Strength

Construction PN-EN 196-1

Overview

Testing of cement compressive (and optionally flexural) strength is a fundamental test in binding material technology. The 28-day result forms the basis for classifying cement into strength classes (32.5; 42.5; 52.5 MPa) and early strength subclasses (N — normal, R — high). Testing is performed on standard mortar prisms of dimensions 40×40×160 mm.

Standard PN-EN 196-1 precisely specifies standard mortar composition: 450 g cement + 1350 g standard sand (CEN) + 225 g water (w/c = 0.50). CEN standard sand is certified natural quartz sand with strictly defined grading, produced by designated laboratories (e.g., SNL in France, Normensand GmbH in Germany). Use of non-standard sand invalidates the result.

Mortar is mixed in automatic mixer according to strict time program, molded in three-part molds and compacted on jolting table (60 cycles in 60 s). After demolding (after 24 h), prisms are stored in water at 20 ± 1°C until test day (2 or 7 days — early strength, 28 days — normal strength).

Testing is mandatory in factory production control of cement (FPC), conformity assessment per PN-EN 197-1 and product certification. Cement plants perform this test daily. Testing laboratories perform it as part of market surveillance and proficiency testing (PT).

Method principle

Standard mortar prisms 40×40×160 mm, after appropriate curing time, are first tested in flexure, then the resulting halves in compression. In flexural test, prism is placed on two supports (100 mm spacing) and loaded with concentrated force in middle of span at rate of 50 ± 10 N/s. In compression test, prism half is placed between two 40×40 mm compression platens and loaded at rate of 2400 ± 200 N/s. Compressive strength Rc = Fc/1600 [MPa], where Fc — failure force [N].

Applications

• Classification of cement into strength classes (32.5; 42.5; 52.5 MPa)
• Factory production control of cement (FPC per PN-EN 197-2)
• Assessment of cement conformity with standard PN-EN 197-1
• Type testing (ITT) of new cement types
• Proficiency testing (PT/ILC) of cement laboratories
• Quality control of special cements (sulfate-resistant, low-heat)

Key parameters

Standard

Standard number

PN-EN 196-1:2016

Title (PL)

Metody badania cementu — Część 1: Oznaczanie wytrzymałości

Title (EN)

Methods of testing cement — Part 1: Determination of strength

Step-by-step procedure

1. Material preparation

   Temper cement, sand and water to 20 ± 1°C. Weigh: 450 ± 2 g cement, 1350 ± 5 g CEN sand, 225 ± 1 g water.

   ⏱ Time: 10 min • 🌡 Temperature: 20 ± 1°C

2. Mold preparation

   Clean three-part molds. Apply mold release oil. Mount on jolting table. Check tightness.

   ⏱ Time: 5 min

3. Mortar mixing

   Pour water into mixer. Add cement. Mix 30 s (slow). Add sand over 30 s. Mix 30 s (fast). Pause 90 s. Mix 60 s (fast).

   ⏱ Time: 4 min

4. Prism molding

   Fill molds with mortar in two layers. After each layer, compact on jolting table (60 jolts in 60 s). Level surface.

   ⏱ Time: 5 min

5. Initial curing

   Place molds in humidity chamber (20 ± 1°C, RH ≥90%) for 24 h. Cover with glass plate.

   ⏱ Time: 24 h • 🌡 Temperature: 20 ± 1°C

6. Demolding

   After 24 h carefully demold prisms. Mark (number, date). Place in water bath 20 ± 1°C.

   ⏱ Time: 10 min

7. Water curing

   Store in water 20 ± 1°C until test day. Water must cover prisms min. 5 mm. Change every 2 weeks.

   ⏱ Time: 2/7/28 days • 🌡 Temperature: 20 ± 1°C

8. Flexural strength testing

   Remove prism from water. Place on supports (100 mm). Load at 50 ± 10 N/s rate until failure. Record failure force Ff.

   ⏱ Time: 1 min

9. Compressive strength testing

   Place prism halves between 40×40 mm platens. Load at 2400 ± 200 N/s rate until failure. Record force Fc.

   ⏱ Time: 1 min

10. Results calculation

    Rf = 1.5 × Ff × l / b³ [MPa] (flexure, l=100 mm, b=40 mm). Rc = Fc / 1600 [MPa] (compression). Result = average of 6 compression values.

11. Assessment and classification

    Compare Rc28 with PN-EN 197-1 requirements: class 32.5 (≥32.5 MPa), 42.5 (≥42.5 MPa), 52.5 (≥52.5 MPa). Check Rc2 or Rc7.

12. Documentation

    Prepare report: cement type, mixing date, curing conditions, Rf and Rc results, classification.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Testing press — crushing hazard, use protective guards
• Cement — irritating to skin and eyes (pH>12), gloves and safety glasses
• Cement dust — use FFP2 mask when weighing and mixing
• Mortar fragments during failure — safety glasses
• Hot water (optional) — for accelerated testing

Frequently asked questions